Altitude compensator



' uw. A. MARSHALL, JR

Aug. '1,l 1945.

ALTITUDE COMPENSATOR File'd March 29, 1943 5 Sheets-Sheet 1 Auug..7, w. A. MARSHALL, JR 2,381,358

ALTTUDE coMPENsAToR 3 Sheets-Sheet 2 Filed March 29, 194s www .Interi/t vww. .Llll

Aug'. 7, 1945-. w. A MARSHALL, JR 2,381,358

` ALTITUDE GOMPENSATOR Filed March 29', 1943 3 Sheets-Sheet 3 long and trouble-free service.

Patented Aug. f 7, y1945 UNITEDY STATES PATENT OFFICE Y ALTITUDE ooMPENsA'ron william A. Marshall, Jr., oak Puk,- m.. assigner to Stewart-Warner Corporation, Chicago, lll., a corporation of Virginia y Application March 29, 1943, Serial No. @80,974

. I (omai-53) My invention pertains to altitude compensa- 6 Claims.

torsand is more particularly concerned with, but not limited to, an altitude compensator for use in aircraft heaters of the internal combustion type.

In the pending application of Lynn A. Williams, Jr., Serial No. 476,429, filed February 19,

1943, there is described an internal combustion type of heater particularly adapted for aircraft, and wherein the iuel supply is controlled by the difference in pressure between the combustion chamber of the heater and the induction tube leading to this combustion chamber.

' This pressure difference increases with increase this pressure difference from increasing withincreases in altitude.

An object of my invention is to provide an altitude compensator which is particularly adapted. but not limited, to use as part oi' the fuel feeding system of an internal combustion heater like tha disclosed in this Williams application.

Another object of my invention is 'tof provide an altitude compensator which is simple, compact, light in weight, and inexpensive'to manufacture, but which is suiiiciently rugged to give Another object of my invention is to provide an altitude compensator which maybe readily adjusted without disassembly, and 1n a minimum length o f time, with only a simple tool such as a screw driver.

Other objects and ladvantages will become apparent as the description proceeds.

In the drawings; y Fig. 1 a view showing my invention applied toan internal combustion type of heater, the heater being shown in'longitudinal section;

Fig. 2 is an enlarged sectional View of the fuel feeding control means shown in Fig. 1, and shows, in elevation, my novel compensator applied thereto:

Fig. 3 is an end view of Fig. 2, taken on the line 8 3 of Fig. 2; and

Fig. 4 is an enlarged view showing my altitude compensator in longitudinal section. u

In Fig. 1, I have illustrated my invention as 'used in connection with the fuel feeding system of an internal combustion type. ot heater. This heater has a combustion chamber I supplied with ycombustible mixture from an induction pipe I2 communicating with the combustion chamber through slots Il. An electrical igniter I6 serves initially to ignite the combustible mixture supplied to the combustion chamber I8, and is ordil narily provided with a thermostatic switch whch disconnects it from its source of electrical current when the heater attains normal operating temperature. A reigniter 4I8 is'provided to insure maintenance of combustion after the igniter I8 has been disconnected from its source of electrical energy. y

The hot products of combustion formed in the combustion chamber I8 ow from the right-hand end of this chamber into a tubular heat exchanger of the hollow iin type. The ends of the hollow iins are sealed, as indicated at 22 and 28. A muiller 26 directs the hot products of combustion into the left-hand ends of the hollow iins, and as the hot gases traverse these iinsjthe heat from the gases is transmitted to the heat exchanger 20. lThe cooled gases -iiow from the right-hand ends of the hollow iins into an outlet chamber 28, which communicates with atmosphere through a discharge fitting 30 and any suitable exhaust pipe which may be attached to the threaded end' 32 of this fitting.

The muiiler 28 has a sheet metal shell 34 pro-' vided with openings 38 forming acoustic couplings `betweenthe gas passages and the interior of the muiiler, which is lled with sound absorbing material 38, such as stainless steel wool or glass wool. The muiiler may be provided with aV nose 4I! forming an empty acoustic chamber connected y by openings 44 to the interior of the main part of A fuel jet 46 isv located in the induction pipe I2 and is supplied with `i'uel by a pressure fuel supply means indicated generally by the reference character 48, and connected to the jet 46 by a pipe 50. The fuel supply means I8 operates on the diiIerence in pressure between the combustion chamber III and the inlet of a ram 52 which is connected to the pressuredevice I8 by a pipe "54.

rPipe 58 connects the fuel supply means 48 with the combustion chamber I0. A pipe 58 connects the fuel supply means with a fuel pump, elevated tank, ,or other source of fuel under pressure.

Referringto Fig. 2, it will be seen that communication between the fuel pipe 58 and a cham- Y ber is controlled by a valve G2 which is moved .to closed position by a lever 88 pivoted on` an adport is urged by a spring The other end of the lever 64 is pivotally connected to an operating rod 12 attached to a disc 14, closing one end of a bellows 16.

, The other end of the bellows 16 is attached t0 the wall 18 of a casing 80 s'o that the interior of the bellows 16 constitutes a variable chamber in communication with the ram 52. That part of the casing 80 which is external of the bellows 16 and disc 14, constitutes a` second variable chamber 82 kwhich communicates through pipe 66 with chamber 60, which extends into the interior of,

as being attached by bolts |04 to the wall'10 of y the casing 80.

av bellows 84 surrounding the valve operating rod 12. The dierence in pressure between the ram 52 and combustion chamber |0 acts over substantially the entire area of the disc 14 and the force thus created acts upon the relatively small cross sectional area of that portion of the fuel chamber 60 which extends into the bellows 84, so

' that the pressure diiierence between the ram-52 and combustion chamber is stepped up and acts upon the fuel in the fuel chamber 60 to force this fuel to the jet 4E.

The combustion chamber l0 and heat exchanger 20 are surrounded by a cylindrical casing 86 which isconnected to an air inlet 88 attached to the usual ram. In the particular heater shown l in the drawings, the same ram and inlet provide the combustion air for the induction tube I2. Ventilating air flows between the heat exchanger 20 and casing 86, and picks up heat from the heat exchanger. The heated Ventilating air ows from the right-hand end of the casing 86 directly vinto a cabin or other space to be heated, or into a duct system having outlets at selected locations. When an airplane provided with such a heater increases its altitude, the pressure drop between the ram 52V and combustion chamber 0 increasesf for any constant mass ow rate,and this would result in increasing the richness of the mixture supplied to the combustion chamber un-y less compensating means be provided. This increase in pressure drop can be prevented fromV airecting the fuel chamber in by providing a vent orifice for the interior of the bellows 16 and pressure responsive means for controlling the eslcape of air through this opening, 'I'he subject matter thus far described is claimed in the aforesaid Williams application, and my invention lies in the particular structure of the altitude compensator and associated valve means for regulating the escape of air from the interior of the bel-'- lows 16.

Referring I nore particularly to Fig. 4, it Will beV seenthat I have provided a tube 30 projecting into the interior of the bellows 16, and provided with a longitudinally extending slot 82. A spool shaped valve 94 is slidable inthe tube 90 'and regulates the escape of air from the interior of the bellows 16 by way of slot 92 and'tube 90. In

the particular position of the valve 04 shown in the drawings, the valve prevents escape of air from the bellows 16 so that the diierential presy sure across the disc 14 is the differential pressure The housing |02 has an end wall |08 provided with an integral nipple |08 into which a sleeve ||0 is threadedly engaged. A screw ||2 has a smooth end located in the sleeve I0 and a tubular nurl I I 4 located in the sleeve I |0, and a ange ||6 on the screw ||2 is clamped between this nut and 'sleeve tp prevent axial movement of the screw I I2, but permitting rotation thereof when a screw driver or similar tool is engaged in the lrerf4 I I8 located in the en d of the screw.

'Ihe threaded end of the screw 2 is located in a threaded tubular support |20 attached to the fixed end wall |22 o; the evacuated bellows |00. A pin |24 carried by this end wall is slidably received in the opening |26 formed in a spring support |28 rigidly clamped between the nut ||4 and sleeve ||0 This pin |24 prevents rotation of the bellows |00 relative to the spring keeper |28 when the screw ||2 is rotated to adjust the spring load. A spring |30 is confined between the spring support |28 and a flange |32 of the head 98. This spring tends to expand the bellows |00 and shift valve 94 to permit the escape of airl through the slot 92 and tube 90. By rotation of the sleeve' ||0 the position ofthe spring keeper |28 can bedetermined, and thus the setting of the valve 94 can be properly adjusted without dismantling the apparatus.

The bellows |00 is collapsed .by the difference in pressure between the interior ofthe bellows and the space |34 between' this bellows and the hous- |08 and must be removed to permit adjustment of the screw I |2` or sleeve ||0. The sleeve ||0 is provided at its upper end with a kerf |40 which can be engaged by a screw driver to permit rotation of this sleeve relative to the housing. vThe device is calibrated in the following manner. A simple adjustment of the screw I I2 determines the pressure exerted by the spring |30, inasmuch as rotating -this screw in eiect lengthens or shortens the bellow |00. Similarly, rotation of the sleeve I0 moves the upper'spring keeper upwardly or downwardly without disturbing the position of the bellows relative to the upper spring keeper |28. Therefore, -rotation of this sleeve lmoves, the valve 84 inwardly or outwardly with-A out changing the spring pressure. Y

As the plane carrying the heater rises to higher and higher altitudes, the absolute pressure in the combustion chamberdecreases and the absolute pressure in the space |34 likewise decreases. This permits spring |30 to expand bellows |00, thereby moving valve 94 to the left and permitting air to escape from the interior of bellows 16. The

leftward movement of valve 94 varies with variations in altitude, and maintains a, constant pressure diierence across the disc 14 with constant mass iiow, and therefore a, constantpressure in the fuel chamber 60 for all altitudes. The combustible mixture delivered to the combustion chamber therefore does not increase in richness as the altitude of the plane increases. These advantages are provided by my novel altitude compensator which is simple in construction, light in pipe B into the combustion chamber I0 may be more than is desirable, at least in some instances. v

weight, inexpensive to manufacture, and sturdy and durable.

It will be appreciated that inward and outward movementl of the valve 94 bleeds air from the interior of the bellows 16, thereby altering the pressure difference across the bellows only "if the rate of escape of air through the valve 94 is.

assises variable pressure, and valve means controlled bycomparatlvely rapid, inasmuch as air is continue i ously entering-the bellows 16 through the'V pipe The result is that the flow of air through In order to avoid this comparatively rapid now of air into the combustion chamber a restriction.

can be introduced in the line 54 or in the line 5G. such an orifice, indicated by the' numeral |42, as being located in the fitting which connects the housing, a spring confined between said housing and the opposite end of said bellows to expand the same, said screw being adjustable to vary kthe'positionbetween said housing and the first named end of said bellows, means for connecting the interior of said housing .with a source of Asaid bellows.V

3. Compensating'means of the class described comprising a fixed support, an evacuated bellows, an adjustable connection between said support and oneV end of said bellows, a spring for expanding said bellows, said spring being vconfined between said support and the other end of said For purposes of illustration I have shown i pipe 54 with the interior of the bellows 16, it being understood that this or a similar orifice can function of the orifice |42 is to restrict the flow of lair through the tube 54 to the interior of the bellows 'I8 so that inward movement ofthe valve 94 will more readily bring about a pressure drop across the bellows. If the orifice is placed in the' line 56, the now of air through the pipe 54 into the bellows will be comparatively free; thus, regardless of the position of the valve 84 the pressure inside the bellows will remain substantially constant.` On the other hand, the suction effect vproduced-exteriorly of the bellows 18 will depend upon the amount of air flowing through the pipe Illl to the orince located in the lineY IB. In either case inward or outward movement of the be placed in the une as 'instead 1f desired. The

said support, said support having an opening slidably receiving va pin attached to said bellows and serving toprevent rotation of said bellowsl with f said screw, a spring for expanding said bellows,

valve 94 effectively controls the pressure dropacross the bellows 16 in the manner previously described.

`While I have disclosed only a single embodiment of my invention, it is to be-understood that -my invention is not limited to the details shown and described, but may assume numerous other forms, and that the scope of my invention is defined in the following claims? I claim: f

1. An altitude compensator comprising an evacuated bellows, a casing enclosing said bellows and in spaced relation thereto, a pipe for connecting said space with a variable source of pressure, a tube connecting said space with an adjacentspace under pressure, said tube having a longitudinal slot in a wall thereof, a spoolshaped valve movable to control communication betweensaid two spaces by way of said tube and slot, a valve stem connecting said valve with said bellows and a spring for expanding said bellows.

2. Pressure responsive means comprising an evacuated bellows, a housing for said bellows, a screw attaching one end of said bellows to said valve means attached to said bellows and controlled by expansion and contraction thereof, said-screw being addustable to vary the pressure vof said spring, and a removable cover enclosing saidscrew. i

5. A compensator of the class described comprising an evacuated bellows, a spring for expanding said bellows, `a supporting member attached to one end of said bellows, said memberl having a partje'ng'agins the other end oi' said bellows to limitfcontraction thereof, a screwengaging said member, a support carrying said screw and bellows, said screw being rotatable to shift the relationship between said support and one end of said'bellows, slidable means between said bellows and support to prevent rotation of said bellows withsaid screw, means interposed between said screw and support to adjust said spring, land pressure control means operated by expansion and contraction of said bellows.

6. An altitude compensator of the class de; scribed, comprising a housing, an evacuated bellows located in said housing, an adjustable screw connecting saidv bellows and housing said screw having a radially projected flange, a sleeve `ro tatably mounted in said housing and receiving one end of said screw, a tubular nut surround'- ing said screw and confining said flange between itself and said sleeve, means for expanding said bellows, a support for said last-named means clamped between said nut and sleeve, and pressure control means operated by said bellows.

' WILLIAM A. MARSHALL, Ja.

Y D l S C L A l E R 2,38l,358.-W'illiam A. Marshall, Jr., Oak Park, Ill. ALTITUDE CoMPENsA'ro-R.

Patent dated Au 7, 1945. Disclaimer Stewart-Warner orporation.

filed Oct. 2, 1947, bytheassignee,

Hereby enters this disclaimer to claims 2 and 3 in said specification.

[Ojci'al Gazette November 11, 1.947.] C

pipe B into the combustion chamber I0 may be more than is desirable, at least in some instances. v

weight, inexpensive to manufacture, and sturdy and durable.

It will be appreciated that inward and outward movementl of the valve 94 bleeds air from the interior of the bellows 16, thereby altering the pressure difference across the bellows only "if the rate of escape of air through the valve 94 is.

assises variable pressure, and valve means controlled bycomparatlvely rapid, inasmuch as air is continue i ously entering-the bellows 16 through the'V pipe The result is that the flow of air through In order to avoid this comparatively rapid now of air into the combustion chamber a restriction.

can be introduced in the line 54 or in the line 5G. such an orifice, indicated by the' numeral |42, as being located in the fitting which connects the housing, a spring confined between said housing and the opposite end of said bellows to expand the same, said screw being adjustable to vary kthe'positionbetween said housing and the first named end of said bellows, means for connecting the interior of said housing .with a source of Asaid bellows.V

3. Compensating'means of the class described comprising a fixed support, an evacuated bellows, an adjustable connection between said support and oneV end of said bellows, a spring for expanding said bellows, said spring being vconfined between said support and the other end of said For purposes of illustration I have shown i pipe 54 with the interior of the bellows 16, it being understood that this or a similar orifice can function of the orifice |42 is to restrict the flow of lair through the tube 54 to the interior of the bellows 'I8 so that inward movement ofthe valve 94 will more readily bring about a pressure drop across the bellows. If the orifice is placed in the' line 56, the now of air through the pipe 54 into the bellows will be comparatively free; thus, regardless of the position of the valve 84 the pressure inside the bellows will remain substantially constant.` On the other hand, the suction effect vproduced-exteriorly of the bellows 18 will depend upon the amount of air flowing through the pipe Illl to the orince located in the lineY IB. In either case inward or outward movement of the be placed in the une as 'instead 1f desired. The

said support, said support having an opening slidably receiving va pin attached to said bellows and serving toprevent rotation of said bellowsl with f said screw, a spring for expanding said bellows,

valve 94 effectively controls the pressure dropacross the bellows 16 in the manner previously described.

`While I have disclosed only a single embodiment of my invention, it is to be-understood that -my invention is not limited to the details shown and described, but may assume numerous other forms, and that the scope of my invention is defined in the following claims? I claim: f

1. An altitude compensator comprising an evacuated bellows, a casing enclosing said bellows and in spaced relation thereto, a pipe for connecting said space with a variable source of pressure, a tube connecting said space with an adjacentspace under pressure, said tube having a longitudinal slot in a wall thereof, a spoolshaped valve movable to control communication betweensaid two spaces by way of said tube and slot, a valve stem connecting said valve with said bellows and a spring for expanding said bellows.

2. Pressure responsive means comprising an evacuated bellows, a housing for said bellows, a screw attaching one end of said bellows to said valve means attached to said bellows and controlled by expansion and contraction thereof, said-screw being addustable to vary the pressure vof said spring, and a removable cover enclosing saidscrew. i

5. A compensator of the class described comprising an evacuated bellows, a spring for expanding said bellows, `a supporting member attached to one end of said bellows, said memberl having a partje'ng'agins the other end oi' said bellows to limitfcontraction thereof, a screwengaging said member, a support carrying said screw and bellows, said screw being rotatable to shift the relationship between said support and one end of said'bellows, slidable means between said bellows and support to prevent rotation of said bellows withsaid screw, means interposed between said screw and support to adjust said spring, land pressure control means operated by expansion and contraction of said bellows.

6. An altitude compensator of the class de; scribed, comprising a housing, an evacuated bellows located in said housing, an adjustable screw connecting saidv bellows and housing said screw having a radially projected flange, a sleeve `ro tatably mounted in said housing and receiving one end of said screw, a tubular nut surround'- ing said screw and confining said flange between itself and said sleeve, means for expanding said bellows, a support for said last-named means clamped between said nut and sleeve, and pressure control means operated by said bellows.

' WILLIAM A. MARSHALL, Ja.

Y D l S C L A l E R 2,38l,358.-W'illiam A. Marshall, Jr., Oak Park, Ill. ALTITUDE CoMPENsA'ro-R.

Patent dated Au 7, 1945. Disclaimer Stewart-Warner orporation.

filed Oct. 2, 1947, bytheassignee,

Hereby enters this disclaimer to claims 2 and 3 in said specification.

[Ojci'al Gazette November 11, 1.947.] C 

